The Congress of Industrial Organizations (CIO) was a national labor organization that formed in November 1935. It was originally called the “Committee for Industrial Organization.” In 1886, thirteen national unions formed the American Federation of Labor, or AFL, which was a labor organization that primarily represented skilled workers. These skilled occupations were referred to in the nineteenth century as “crafts.” Although the AFL did include unskilled laborers in its membership, the federation favored skilled craft unionism. But as America became more industrialized in the early twentieth century, mass production industries emerged, requiring a larger, less-skilled workforce in comparison with the number of traditional AFL members in craft unions. The CIO formed to promote the organization of workers in mass-production industries. Eight member unions that were in the AFL formed the CIO. Original founding members included major national unions representing mine workers, typographical employees, and the garment trades. The American labor movement was split in the mid-1930s through the mid-1950s between the AFL and the CIO regarding how best to organize workers, and how best to represent those worker unions. Eventually the ideological differences between the two organizations lessened, until they merged as the unified AFL-CIO in 1955.